An apparatus for separating organic material from inorganic material is known from German Patent No. DE 44 15 647 C2 corresponding to U.S. Pat. No. 5,641,397 and to European Patent No. EP 0 707 520 B1. The known apparatus includes a container having a vertical axis. The container has a cross-section which enlarges in sections in a downward direction. A feeding apparatus for introducing the polluted inorganic material into the container is arranged in the upper portion of the apparatus. A discharging apparatus for the separated cleaned inorganic material is located in the lower portion of the container. The discharging apparatus is designed as an upwardly inclined spiral conveyor. The apparatus includes a unit for discharging the organic material. This unit is arranged in the upper portion of the container, and it includes an edge via which cleaning water and organic material are discharged. A charging apparatus for cleaning water is arranged in the lower portion of the container and above the discharging apparatus for the separated inorganic material. The charging apparatus includes a aperture plate including a majority of openings, nozzles, and the like, being distributed about the cross-section such that one attains an upwardly directed flow being distributed about the cross-section. The cleaning water is fed into the apparatus at such an amount per time unit and it is distributed by the openings of the plate in an upward direction such that there is a fluidized layer above the aperture plate. The fluidized layer is to be understood as a fluidized bed by which the organically polluted inorganic material is subjected to a movement which is typical for a fluidized bed. This typical movement causes the sand corns to contact the wall of the container such that the organic material sticking to the inorganic material is detached from the inorganic material. Due to the cleaning water flowing in an upward direction, the organic material is guided thereby in an upward direction. The fluidized bed substantially differs from a stirred fixed bed in which the sand corns cannot freely move. The fluidized layer typically has a certain height in the container, the height being watched by a pressure cell. The signals of the pressure cell may be used to control the discharging apparatus for the separated inorganic material. To enable the material to be discharged to reach the region of the discharging apparatus, there is bypass which may be realized in various ways. For example, it may be realized by an opening in the center portion of the aperture plate, the arrangement of a bypass conduit or other openings through which the cleaning water may flow in an upward direction and the cleaned sand may flow in the downward direction. A stirring tool is arranged in the container. The stirring tool includes stirring arms which may be arranged in the lower portion of the fluidized layer and/or in the lower portion of a deposit chamber for the organic material. The known apparatus effectively separates organic and inorganic material. However, the fluidized layer is exclusively produced by the introduced cleaning water such that it is necessary to provide respective amounts per time unit. The velocity of the upwardly streaming water (superficial velocity) is approximately between 5 to 15 m/h. The stirring arms of the stirring tool which are arranged to rotate in the lower portion of the fluidized layer and/or in the lower portion of the depositing chamber for the organic material prevent the formation of channels in the lower portion of the fluidized layer, on the one hand, and they loosen the organic material located above the sand layer, on the other hand, such that polluted material introduced by the charging apparatus may still move through the organic layer to reach the region of the fluidized sand layer.
A method and an apparatus for removing sand from waste water including sand and organic materials in a stationary container are known from European Patent No. EP 0 713 418 B1 corresponding to U.S. Pat. No. 5,811,016. A feeding apparatus is arranged in the upper portion of the container. A discharging apparatus for the separated inorganic material is located just above the lower portion of the container. The discharging apparatus is designed as a spiral conveyor. A feeding conduit for fresh water is also located in this portion. By this feeding conduit, fresh water is subjected to a rotary flow in which the specifically lighter organic material moves in an upward direction towards an overflow, while the specifically heavier sand corns sink towards the bottom of the container to form a pile of sand which is mechanically stirred by a stirring tool such that the sand corns get in frictional contact with one another to remove organic material sticking to the sand corns. The removed organic material is transported in an upward direction by the upwardly directed flow produced by the introduced fresh water. In this way, the polluted sand contained in the fixed bed is mechanically stirred, and it is only removed in an amount which ensures a predetermined minimum level of the deposited sand. Consequently, the cleaning effect is substantially caused by the mechanical movement of the sand corns in the fixed bed by the stirring tool. For this purpose, the stirring tool needs to have appropriate power.
A removal method for mineral sand from a mix of water, organic components and sand to be treated is known from German Patent Application No. DE 198 44 006 A1. The mix is introduced into a deposit container from above. Small bubbles of air move through the mix from below in an upward direction such that the organic components and the sand are separated in a vertical direction depending on their density. Due to its greater density, the sand is removed in a controlled way. The mix of sand, water and organic components may also be mechanically stirred during the movement of the air bubbles through the mix. The sand deposited in a fixed bed in the bottom portion of the container may be used to determine the torque to be supplied for stirring. The fluidity of the mix may be controlled by additional water supply from above. The apparatus may also fulfill the function of a sand separator or a sand catcher. Due to the small bubbles moving through the mix of sand, water and organic material, the mix is respectively moved which leads to the desired separating effect.